1. Field of the Invention
The present invention relates to an electron emission display, and more particularly, to an electron emission display having an anode electrode which is coupled to a phosphor layer to receive a high voltage required for accelerating electron beams.
2. Description of Related Art
Generally, electron emission elements can be classified into those using hot cathodes as an electron emission source, and those using cold cathodes as the electron emission source.
There are several types of cold cathode electron emission elements, including Field Emitter Array (FEA) elements, Surface Conduction Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and Metal-Insulator-Semiconductor (MIS) elements.
The electron emission elements are arrayed on a first substrate to form an electron emission device. A light emission unit having phosphor layers and an anode electrode is formed on a second substrate. The electron emission device, the second substrate, and the light emission unit establish an electron emission display.
In the electron emission display, there is provided an anode electrode for directing the electrons emitted from the first substrate. The anode electrode receives a high voltage required to accelerate the electron beams, thereby reducing the extent to which the surface of the phosphor layer is charged by the electrons.
The anode electrode is formed of a transparent conductive material such as indium tin oxide (ITO) or a metallic material such as aluminum. The anode electrode is coupled to the phosphor layers facing the first substrate. The anode electrode functions to heighten the screen luminance by receiving a high voltage required to accelerate the electron beams and by reflecting the visible rays radiated from the phosphor layers to the first substrate back toward the second substrate.
The anode electrode is formed by (1) forming an interlayer formed of a polymer material that will be vaporized during a firing process; (2) depositing a conductive material, for example, aluminum, on the interlayer; and (3) removing the interlayer by vaporizing the interlayer material through fine pores of the conductive material.
The yield and performance of the anode electrode are greatly affected by a deposition thickness of the conductive material, a distance between the anode electrode and the phosphor layer, a distribution of fine pores in the conductive material, and other similar factors. For example, if the anode electrode lacks a proper distribution of fine pores (e.g., has a relatively low density of the fine pores), it may be easily damaged during the firing process for removing the interlayer, and the light reflective efficiency may be reduced.
That is, if the anode electrode is too densely deposited to have the proper distribution of fine pores, the interlayer material cannot be completely vaporized through the fine pores during the firing process, thereby causing the anode electrode to swell.
As a result, a portion of the anode electrode peels off. The damaged portion of the anode electrode cannot properly accelerate the electron beam from the first substrate, and thus the light emission efficiency of the phosphor layer corresponding to the damaged portion of the anode electrode is reduced.
By contrast, when the density of the fine pores is too high, the light reflective efficiency of the anode electrode is lowered such that the luminance of the image deteriorates.